Middle and low-voltage electric power cables, such as an electric power cable 200 transmitting voltages less than 26/35 kV (U0/U) as shown in FIG. 3, generally comprise: a conductor core 201, an insulation layer 202 covering the conductor core 201, a semi-conductive shield layer 203 covering the insulation layer 202, a metal shield layer 204 covering the semi-conductive shield layer 203, and an outer protection layer 205 covering the metal shield layer 204.
There are two types of cold shrinkable termination products for middle and low-voltage electric power cables in the prior art.
The first type of cold shrinkable termination product comprises an insulation tube and a layer of stress control glue and a stress control tube provided inside the insulation tube. When the cold shrinkable termination is mounted onto a processed or exposed end of the electric power cable, the stress control glue and the stress control tube is wrapped on the exposed semi-conductive shield layer and insulation layer of the electric power cable. In this way, local electric field concentration is prevented at the exposed ends of the electric power cable by the double layers of stress control material.
The second type of cold shrinkable termination product comprises a commonly used geometric stress control cone. When the cold shrinkable termination is mounted onto a processed or exposed end of the electric power cable, silicone oil or silicone grease should be used as a filling agent that fills a gap between the insulation tube of the cold shrinkable termination and the electric power cable. The use of silicone oil or silicone grease as the filling agent, however, is not acceptable in the some countries.
With regard to the first type of cold shrinkable termination product, since double layers of stress control material are used, the manufacturing cost is high and the structure is complicated.
With regard to the second type of cold shrinkable termination product, since the stress control cone and the silicone oil or silicone grease used as the filling agent are employed, similarly, there are the drawbacks of high manufacturing cost and complicated structure. In addition, this type of cold shrinkable termination product is not in conformity with corresponding technical regulations of certain countries, resulting in limited applications.